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Make-ahead Mashed Potato Casserole

30 Mins Cook
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NomNom Recipes 26 1

The Mashed Potato Casserole is a delicious yet super convenient way to make mashed potatoes ahead of time! A layer of cheese and bacon keeps the mashed potatoes from drying out as it warms in the oven, turning that humble side into something nastier and more decadent. Oh, the power of cheese (plus bacon)!

Freshly prepared or assembled in advance and reheated as needed. Serve in place of plain oil mash.

NomNom Recipes 26 2
Mashed Potato Casserole – NomNomWow

Make-ahead mashed potato

With the holidays fast approaching, I thought it was time to share my favorite way to make mashed potatoes ahead of time.

The problem with making mashed potatoes ahead of time is that you can’t just reheat it in the microwave or oven. You might think a little milk and a good mix will do the trick. But I can tell you, it’s the path to a mouth full of fudge horror.

While there are practical ways to successfully reheat cold mashed potatoes*, the Big Pan Creamy Mashed Potato Casserole won the award in the easiest and most convincing way I know!
It also won the Least Effort of the Day award because you literally put the pre-assembled dish in the oven. It’s a 10/10 win-win – nothing beats your holiday party menu! !

  • How I reheat plain mashed potatoes: cold mashed potatoes in hot cream (recipe here, but be careful, more work for the day) or dipped in heavy piping bags in hot cream boiling water, tricks used by caterers (Check out my Instagram demo here).

Is there such a thing as too much bacon??

Confession: I feel like I’m a little clumsy with the bacon in the photo, and I’m a bit lacking in material for the recipe video! ! So written recipe cards are a happy medium.

But actually, if you look at the photo below, it looks tempting, almost covered in bacon. And… is there such a thing as too much bacon?
? (and)

What you need for Mashed Potato Casserole

Here’s what you need to make Mashed Potato Casserole:

  • Potato – Floury and all-rounder potatoes work best to achieve a fluffy yet creamy mash without fussing with potato ricers and other gadgets.
    – Australia: the cheap dirt-brushed potatoes sold everywhere (called Sebago) are ideal
    – US: Russet
    – UK: Maris Piper
  • Milk – Our liquid to loosen the potato up to form mash. If making ahead, we add extra (see How To Make section for more).
  • Sour cream – I prefer using sour cream rather than cream in mashed potato casserole because the slight tang makes a nice counterpoint to all the other richness going on here (butter, cheese, bacon). It doesn’t make it sour in the least. It sort of adds creaminess into the mash without adding cloying richness. Does that makes sense??
  • Butter – Mash without butter is not mash. #strongopinions!
  • Cheese – I use a combination: Mozzarella for excellent melty-cheesy-stretchiness. Then Red Leicester for flavour (it’s savoury and a bit sharp, like aged cheddar), and to add a lovely orange hue to the mash surface. If you’re in the States, your orange cheddar is ideal here. Otherwise, use any melting cheese you like (colby and Monterey Jack are other personal favourites). If you opt to use mozzarella as your main cheese, add a handful of parmesan for flavour because mozzarella alone is actually quite bland and lacks saltiness.
    Shred your own – One of my five non-negotiable rules stated loudly on the first page of my cookbook is, “Always shred your own cheese”! Store-bought pre-shredded cheese is coated in anti-caking agents which prevent it from melting as well as freshly-grated. I use a standard box grater for the work.
    Pack your cups of cheese – For consistency I prefer weight over volume to measure cheese. So I’ll weigh a hunk of cheese before grating it. But if you are using cup measures, be sure to pack your cups tightly when measuring the shredded cheese otherwise you will be short. Nobody wants to be short on cheese, ever!
  • Bacon – For sprinkling over the casserole surface. Note: I always use streaky bacon. Because fat = flavour! Also, fatty bacon crisps up and colours better, without drying out.
  • Green onion – For a touch of oniony freshness and colour.

How to make Mashed Potato Casserole

No rocket science here. We make mashed potatoes, spread it on a baking sheet, top it with cheese, bacon, stop here if it’s quick. Finally, the day you make it, bake it!

  1. Cut potatoes – Peel and cut the potatoes into even sized pieces.
  2. Boil until soft – Place the potatoes in cold salted water. Bring it up to a boil over high heat then reduce the heat down to medium high or medium so it is simmering rapidly. Cook for 15 minutes (no lid) or until the potatoes are very soft. They should fall apart when you jab it with a fork.
  3. Mash – Drain the potatoes well in a colander and pour them back into the empty pot. Mash with the butter, milk, sour cream and salt. MAKE-AHEAD ADJUSTMENT – If you are making this dish with the intention of serving it the next day, then add an extra 2/3 cup milk. The mash will seem too loose, but this is intentional. It is to factor in the fact that mashed potato firms up when refrigerated overnight. So once reheated, it has the same consistency as when it is freshly made! Potato masher – I like to use a potato masher that is like a round disc with holes in it, as pictured above. It’s the fastest and most effective tool for a smooth mash without using a potato ricer (which I reserve just for Paris Mash, when seeking that next-level-luxe, ultra-smooth, 3-Michelin-restaurant result!).
  4. Spread in a casserole dish.
  1. Top with the cheeses and bacon. (Yes you eagle-eyed spotters, I was short on bacon for these shots )
    For make ahead – At this stage, the assembled dish can be popped in the fridge for up to 3 days. Just take it out of the fridge 2 hours ahead so it has time to de-chill. This will make it reheat faster and more evenly in the oven.
  2. Cover with foil then bake for 20 minutes at 200°C / 400°F (180°C fan), if freshly made. Add an extra 15 minutes if you’re reheating a make-ahead casserole you prepared the day before.
  3. Uncover – Remove from the oven and bake for a further 10 minutes until bubbly and golden.
  4. Voila, ready to serve! Crack through that molten cheese surface and marvel at how creamy the mash underneath is!

How to serve Mashed Potato Casserole

This is a dish designed to be a side. (I know we can all picture it moonlighting as a standalone dish after a big night on the turps or a shocking day at work, but it’s meant to take the place of traditional plain mashed potato, I swear.) Because actually, though this has cheese and bacon on it, underneath is all creamy plain mashed potato.

So place it on the table or on the buffet alongside the mains and let everybody dig in and help themselves! Try to get in first though. Because you know full well the first in line are going to take more than their fair share of that cheese bacon topping – and we know full well we also cannot blame them

Make-ahead Mashed Potato Casserole

Make-ahead Mashed Potato Casserole

The Mashed Potato Casserole is a delicious yet super convenient way to make mashed potatoes ahead of time! A layer of cheese and bacon keeps the mashed potatoes from drying out as it warms in the oven, turning that humble side into something nastier and more decadent. Oh, the power of cheese (plus bacon)!
prep time
30 Mins
cooking time
30 Mins
total time
1 hour



  • 1.75kg/ 3.5 lb potatoes (Sebago (Aus), Russet (US), Maris Piper / King Edwards (UK)(Note 1)

  • 1 tbsp cooking / kosher salt , for cooking potatoes

  • 2/3 cup milk (preferably full fat/whole milk but lite ok)

  • 2/3 cup EXTRA milk , for make-ahead option only (Note 2)

  • 75g / 5 tbsp unsalted butter , cut into 1cm / 1/2″ cubes

  • 1/2 cup sour cream (or yogurt), full fat best

  • 1 tsp cooking/kosher salt , or to taste

  • 1 1/2 cups (tightly packed) mozzarella , freshly shredded (Note 3)

  • 1 cup (tightly packed) Red Leicester, cheddar or other flavoured cheese(Note 3)

  • 200g / 6 oz bacon (streaky), chopped (Note 4)

  • 1/4 cup green onion , finely sliced




Place the bacon in a cold nonstick skillet over medium heat (without oil). As the pan heats up, the bacon fat will melt away. Once you see bacon grease melting, increase the heat to medium-high and stir for 3 minutes or until browned.
Wipe up with paper towels.


Potatoes - Peel and cut into 3cm pieces.
Boil - In a large saucepan, add water to 10 cm / 4 inches above the potatoes. Add 1 tablespoon of salt. Bring to a boil over high heat then reduce heat and simmer quickly for 15 minutes or until potatoes are very tender (test by pushing with a fork and they should fall apart).
Drain and return to pot. Leave to stand for 1 minute, shaking the pan occasionally to promote evaporation.
Mashed Potatoes – Add milk (including premade extra milk), butter, sour cream and 1 tbsp. salt. Press until smooth. (Don't use a food processor, blender or whisk, it will make the food sticky!


Fridge – Allow to fully cool on the counter then cover tightly with cling wrap and refrigerate.
Dechill – Take out onto counter 2 hours prior to reheating.
Bake for 20 minutes (if freshly prepared) or 35 minutes (prep option).
Bake uncovered - remove foil and bake an additional 10 minutes, until cheese is bubbling and golden.
Serve – Sprinkle with green onions and serve! It stays warm for 20 minutes thanks to the protection of the cheese. Ah the power of cheese!


Potatoes – Any starchy or all-rounder potatoes suitable for making mash will work great. Extra milk for make-ahead option makes the mash looser to factor in that mash firms up when refrigerated. This is the amount required so that the reheated dish ends up with the same consistency as when it was freshly made! Cheeses – Mozzarella for excellent melting qualities, plus Red Leicester or US cheddar for colour and flavour (sub with other cheese of choice like colby, gruyere, Swiss, tasty). SHRED YOUR OWN for the best result! Store-bought pre-shredded is coated with anti-caking agents so it doesn’t melt as well. PACK your cups tightly when measuring shredded cheese, else you’ll be short. And nobody wants to be short on cheese, ever! Bacon – You need to use streaky/fatty bacon to use this no-oil method of cooking bacon. If you use lean bacon, you will need to preheat oil. I know which option I prefer! 🙂 Dish – A 2 litre / 2 quart baking dish is the ideal size, it will be filled to the brim. A 23 x 33cm / 9 x 13″ dish (3L/3 qt) works fine too – will be filled about 2/3 of the way up. Make-head – Keeps for 3 days in the fridge, uncooked, fully assembled except for the green onion. Be sure to take it out of the fridge 2 hours prior to reheating to take the chill out of the it so it reheats more evenly. Freezing – A former team member reported excellent results freezing the assembled dish, thawing then reheating. But I never tried it myself – I will come back and update if (no, when!) I do. Leftovers will keep for 3 days, but the mash won’t be as creamy. Consider using it to make mashed potato cakes instead! Nutrition per serving assuming 12 servings, as part of a larger banquet.
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